Flexible strain sensors have attracted great attention due to the urgent demands from the increasing development of stretchable devices, including biomedical devices and wearable devices. Many sensing materials and structures have been developed as flexible strain sensors. Using conventional metal strain gauges as flexible strain sensors was limited by the metal gauge's tough mechanical properties and working range (<5% strain) compared to the strain to be measured in most situations for wearable devices.
What is needed, therefore, is a flexible strain sensor that can overcome the above disadvantages.